I thought I deleted one single text message and I have list all texts from this person. How might I recover those?

The only way of recovering a deleted text message is on the off-chance you had a back-up stored which included this text message however that would mean erasing your phone and setting it up with the new back-up, which can be very time-consuming, plus you need to be confident your text message is actually in this back-up and you have one in the first place.

If you backed up your phone now it wouldn't include said text message but for future reference here is how to update your phone

How to back up your iPhone, iPad and iPod touch – Apple Support